I'm having an *exterior* house painting crisis: what is the impact of using oil-based primer beneath stain?

Our painter is recommending it for consistency of stain color (it makes sense given the circumstances, which I'll spare you) but is using an oil based primer in any way *wrong* for a stained cedar house? Isn't it essentially...painting the house?

(Plan B is to ask the paint store to retint for consistency of color which is necessary because of someone's historical short attention span. House is two different colors currently, basically.)

So in furniture finishing, where you have woods that are prone to absorbing stains at different rates, people will often put a layer of (dewaxed) shellac on first as a sealer. So it's certainly not unheard of, and oil based primers can be (roughly) clear.

If you don't trust your painter's judgement maybe ask a finish vendor or a cedar shake/shingle vendor?posted by straw at 10:23 AM on August 5, 2014

Primers are designed to seal the substrate surface, in this case, your house. Oil based primers are water resistant. An oil based primer coat would seal the wood, and the stain would float on the surface of the primed substrate. It would make the stain uniform, and make the stain stronger at the surface, but you are correct, it would seal the wood surface. Stains differ from pigments inthat they are designed to be absorbed into the substrate. I hope this is helpful.posted by effluvia at 10:35 AM on August 5, 2014 [1 favorite]

Piggybacking on what effluvia said but would also like to clarify that no, primer is not the same as paint and especially not when we're talking about oil and especially doubly not when we're talking about oil applied to wood.

The primer will cover some blotchiness in the wood and provide a more uniform finish. This assuming you're using a solid bodied stain (which you probably are). If it's a semi-transparent stain well, it would still probably be fine though it might look a little more opaque.posted by Tevin at 10:42 AM on August 5, 2014 [1 favorite]

If we use primer...in some way, are we going from a stained house to a something else house?

Because if paint had been an option, I might have gone yellow (sorry for anyone who just fell back in horror). I chose stain because it was consistent with what was done before, but it seems in retrospect I could have gone with anything.

That's not a big deal or anything -- I'm just trying to wrap my head around what this does to the wood and what it means for the future.posted by A Terrible Llama at 10:54 AM on August 5, 2014

Oh, and I trust the guy, it's just that everybody's got a horror story about the time they 'trusted the guy' so I'm being cautious.posted by A Terrible Llama at 10:55 AM on August 5, 2014 [1 favorite]

Well OK now we're getting into semantics a little bit because 'stain' is kind of a tricky term. In paint there are essentially three different components : base, solids, and additives. A paint is paint because it has a certain ratio of solid to base. It's paint-ness is derived from its higher solid base to solid ratio.

Now a stain is a stain because it has a higher base (in this case, oil) to solid ratio than paint. However, the threshold from where paint ends and stain begins is kind of blurry and varies from who you talk to. I'm sure there's an exact ratio somewhere but if there is I don't know about it. But the point is you can have a stain that reveals a lot of the woods surface and character or a stain that hides most of it, or something in between.

Anyway - it depends on what you're going for. Do you want a natural looking finish? Do you want durability? Do you want something that kind of blends in?

Also I have to STRONGLY advise against exterior yellows. Unless pigmenting technology has changed dramatically in the six years since I have worked in a paint store (and it might have!) yellow pigment used in paint fades very quickly when exposed to direct sunlight. So that's something to keep in mind.posted by Tevin at 11:04 AM on August 5, 2014 [1 favorite]

I asked a similar question at my paint store last week. The natural cedar shingles on my house have weathered very unevenly, leaving three distinct wood shades where the siding has gotten different amounts of sun and rain. The very knowledgeable owner said that I definitely shouldn't prime unless I wanted to follow primer with paint...which is an acceptable choice but a very different finish. He said that a solid stain would still penetrate the porous wood, and would give a matte finish hiding whatever is underneath. Solid stain really won't hide texture as much as paint does, but it does hide variations in the underlying shades. He said that a less opaque stain wouldn't fully even out the color.

Your situation is different from mine, though. I second straw's suggestion of asking a paint or shingle dealer. You might want to take a picture and show them.posted by wryly at 11:23 AM on August 5, 2014

The very knowledgeable owner said that I definitely shouldn't prime unless I wanted to follow primer with paint...which is an acceptable choice but a very different finish. He said that a solid stain would still penetrate the porous wood, and would give a matte finish hiding whatever is underneath.

I think what we're facing is a little heavier than just different weathering, we've definitely got that too, but what we're facing is a house that is currently half-red (stain) and half-grayish (stain) or something. It's not totally obvious when you face it straight on, but the previous owners did like a third of the upper part of the house and then, I don't know, went inside to mis-wire something, probably.

We are painting it a dark brown and while it looked nice over the gray (I saw what they'd started this morning), the painter (not the owner but the painter) called just now and said when he painted the brown over the red, it had a greenish cast and he felt like I wasn't going to like it -- that it just wasn't the nice brown we were talking about as he painted this morning. I believe him; I'm glad he called me. I'm sure he's right.

I'm at work so can't look at it right this minute but was hoping I could make a decision so they could get the primer, or get the tint redone, in time to get them back tomorrow. They bailed for today.posted by A Terrible Llama at 11:37 AM on August 5, 2014 [1 favorite]

I would go with a primer tinted brown like the finish, and then use brown paint, not stain. You'll get a solid brown color and the combination of primer and paint will cover all the past sins. All stains are transparent to a greater or lesser degree, and that's probably what's causing the discoloration in the part where they tried it out. If they continue that course, the house will still have two different shades. You need the primer plus paint to cover it.

The only exception would be if you use a paint like Sherwin Williams Duration, which needs no primer (although it might need two coats in your case). It's highly durable because of polymers they mix in, and has a lifetime warrantee for as long as you own the house (IOW free paint if you ever have to paint again). It's also pretty expensive.posted by beagle at 12:10 PM on August 5, 2014

I just talked to the painter and he said they'd had a Sherwin Williams rep come out and look at it and they think that two coats of stain will be sufficient. He said there will be some variances because there's more weathering on one side of the house than the other, but that once they had gotten two coats on and let it dry the greenish tint disappeared. I'm going home to look at it soon and will look at again in light in the morning, but I'm hoping it will turn out okay.

The painter wasn't kidding. This dark brown color looks Frankenstein green over the red. I have to look at the two panels with two layers tomorrow AM - the area they've painted is in the shade. The area they painted over the gray part looks awesome and perfect.

My new, additional problem is that we took down all the shutters, because the shutters looked cheesy to me, and the wood behind the shutters is unsurprisingly fresher than the wood behind it -- meaning there's sort of a shutter-ghost effect I'm going to have to figure out how to deal with/live with.

Having thought about it overnight I'm kind of thinking maybe I should go with the primer because it will maybe smooth out some of those texture discrepancies between the covered wood from where the shutters were removed and the more weathered wood, as well as solve the issue with the color.

I looked at the color in the overcast morning light and it looks okay. Now I'm filled with self-doubt about what to do and crossing my fingers that it's raining enough that they won't work today.posted by A Terrible Llama at 3:35 AM on August 6, 2014

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